Temperature difference between inside and outside of the grow tent means poor ventilation?

Hey everyone. New grower here. Any input would be greatly appreciated.

I currently have a small 2’x2.5’x7’11” grow tent that’s ventilated with an AC Infinity Clouldline T4 set to 3 on the “off” or baseline setting. I also have a small Vornado air circulator on the floor of the tent.

One thing I’ve noticed is that there is about a 6 to 8 degrees F difference between the temperature reading for the sensor inside the tent and the one outside. I’m wondering if this normal? Does this indicate that I don’t have enough ventilation, or the air inside the tent isn’t being circulated enough?

In other words, is the temperature inside the tent supposed to be more or less the same as the ambient temperature in the room?

Thank you


Tents are usually warmer just from light radiation and power supplies.
Is the sensor(thermometer) under the lights?
I try to pace my thermometers closer to the soil than the tops of the plants.

Btw, welcome to the forum.


welcome to the community, i do the same as @Spiney_norman


Thanks so much y’all.

My sensor is hanging at slightly lower than the canopy level now which is about 2 feet from the led light. Definitely will try to lower it closer to the pot, and observe the readings.

The concern I had was that maybe the Vornado doesn’t have enough space to get good circulation going and most the air flow is going directly from my intake vent to the carbon filter without the fresh air sufficiently being mixed up with the existing air. I’m considering adding another fan to the top of the canopy.

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Think about how a black car outside in the sun will get much hotter than the surrounding air.
Likewise a thermometer (or just the sensor) will get a few degrees hotter in the direct light of the tent.
LEDs don’t radiate nearly the same type of light as the sun, but they can raise the temp a few degrees when stuff is near.


That definitely makes sense.

@kropotsmokin Hola amigo!!! Welcome!! Do you have any openings at the bottom of your tent to draw in fresh air to feed the circulation? Otherwise your just blowing around the same air your lights cooking lol.


I keep my AC Infinity sensor at canopy level, and I have a hygrometer at pot level, and another hygrometer in the closet the tent is in to monitor difference between room temp and tent temp. I do notice a difference in temperature between the 3 sensors (i.e. the sensor at the top is between 2 - 4F higher with lights on than the one at the bottom, bottom one is very similar to outdoor hygrometer then). Speed 3 on the AC Infinity might be a bit too low. I started off with 3 at the beginning of the grow, and gradually increased to 5, to 7, now I’m at 9 in flowering.

I would add the fan at the top of the canopy if you don’t already have one. While you’ll only see a very small difference to your temps with it, it’ll help with drying any wet spots on the leaves once the plants really grow and start getting bushy!

Best of luck with your grow! :smiley:


Lots of really great points. I’m still in the veg phase with a single plant that’s been suffering through all sorts of blunders on my part, but thinking I need to bump up the fan a bit regardless.

I’ve been struggling through trying to get my hands on a Cloudray S6 fan for the top of the canopy with the whole shortage fiasco. :sweat_smile:

The reason I’m concerned about fresh air not getting mixed enough with the tent air is that if you look at the diagram, due of space limitations the carbon filter more or less sits above the intake duct, and it seems possible that the fresh air could largely just be going through the filter. I can’t use the other side for the intake because that’s up against a cabinet. The Vornado fan does a good job of circulating air when placed in a room, but I’m not sure how well it works in a confined space like this.


Welcome dood

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Infinity setup directions show that either a push or pull through the carbon filter is acceptable. I am pushing mine this year to save headspace. I have a fan blowing in air through the bottom vent, the infinity sucking out air and then will attach the carbon filter outside the tent when things get smelly. I think this configuration is probably less efficient-there is a reason I dropped out of engineering. Hopefully someone that knows about pressure drop and all that jazz can weigh in.


Finally got my hands on a Couldray S6 fan for the top of the canopy and the difference is huge.

Before installing the top fan, I was seeing a lot of tacoing and other heat stress signs on the upper leaves. The temperature difference between the inside and outside the tent is down to about 4 to 5 degrees F now. This is also allowing me to reduce the power on the lower Vornado fan which was causing wind burn on the lower leaves while not giving enough ventilation to the upper ones.

Thanks everyone for your input and suggestions.


Just thought I’d pitch in to tell you that I’m in a similar position to what you’re in. I could only use 1 intake port since my tent is in a corner, so the back and other side are completely blocked off. I think as long as you have the fan at the bottom near the intake pushing that air around it should be fine. I have 3 plants and all seem to be doing equally in health, I can’t say the one that’s opposite from the intake is doing any worse than the one that’s directly near the intake.

I also have the same ‘issue’ you have with the carbon filter being so close to where the intake is as you showed in your diagram. Again, I can’t say I’ve seen any negative effects from this. Just thought I’d post maybe it will ease your mind a bit :slight_smile:

Glad you managed to get your hands on the fan for the canopy so quickly :slight_smile: Yep, 4 - 5F above room temp with lights on sounds about right :slight_smile: Best of luck with your grow!

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Appreciate all your input. I readjusted the floor fan to be better positioned to move around the fresh air coming from the intake duct. My plant is doing a lot better with the increased air circulation. :grinning:

In your experience, does heat stress/poor circulation make a plant more susceptible to light burn?


That’s awesome! Glad to hear the plant is doing better! :smiley: It’s amazing how quick they will react (both positively and negatively) to changes around them.

Well, I’m not too experienced as this is my first grow (I’m almost 4 months in, currently 5 weeks into flowering) but I think that yes, there is a link to ventilation/and especially heat stress to light burn only if the lights are not positioned properly. I say this because I have 3 plants in my tent, 2 lean more towards the sativa side, while one is more indica and shorter. One of the sativas got way too tall and is only 12" away from the light, and I’m getting top scorched leaves slowly which are getting worse by the day :frowning: The other sativa (which is shorter) and the indica (which is 9" shorter than the scorching sativa) are showing no signs of this whatsoever (they are showing heat stress symptoms but that’s due to temperature and lowering humidity). Best advice I can give is flip earlier than you think, when people say the plants will double to triple in size they’re not joking! The flowering stretch is brutal when you’re seeing your plants grow around an inch a day and you’re running out of headroom to raise the lights!

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It never gets old to tie down a branch and check on it a couple hours later to see the leaves have reoriented to the light. :smile:

That’s been my experience so far too. I had to dial back the lights because all the new growth was bleaching, but once I got my air circulation fixed, the plant is doing fine with full power lights at the same distance as when they were getting light burned.

I’m already having problems with this. I didn’t know topping or training my plant were a thing for the first month of the plants life, so now it’s a very tall plant with one main stalk. I’ve been doing my best to lower the canopy with LST, but already feeling like I’m going to run into height issues in flowering.

Good luck with your grow!

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Indeed! The plant training is definitely the funnest part in the grow in my opinion. I love seeing how they react to the training I’m doing. You definitely should experiment more with LST and topping on your next grow. Apart from making the most out of your space, it will help with air circulation to the buds too having more smaller colas rather than one big one!

Yeah same here, I was almost at full power a couple of weeks ago but I had to dial back to 80% when I saw how close the sativa dominants were getting to the light. Good thing I did too cause the top leaves are burning as it is, let alone at full power! x_X I’m really happy for you that you got it sorted so easily, I’ve been struggling with it for the past 3 weeks now and it’s only getting hotter since summer is coming, so it’s only aggravating the problem :confused:

Ouch, as someone with first hand experience with your problem, I really feel for you. What I would try doing if I was in your position is the tie-down method. Something along the lines of this:

or this:

Just always bend from the top softer growth first and not the woody stem at the bottom. I used a scrog net to try keeping height lower (I have a manifold going with multiple smaller colas), but I don’t think it will do you much good since you have one big cola instead.

Thanks! Hoping I make it to harvest cause the heat is getting worse here. Got 2 plants that should be done in about 5 weeks, so fingers crossed (the other plant has longer…). Best of luck to you too mate! Hope we both get a bountiful harvest :slight_smile: